how to span a 3*1 vector into a 3*3 skew symmetric matrix ?
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Stanley Cheng
el 18 de Jun. de 2014
Editada: Thanacha Choopojcharoen
el 12 de Oct. de 2023
Hi everyone, as the title,
x=[a b c]' is a 3*1 vector, and its 3*3 skew symmetric matrix is
X=[0 -c b ;
c 0 -a ;
-b a 0 ];
what command is all right to make it in Matlab ?
THX very much!
Cheers
2 comentarios
Thanacha Choopojcharoen
el 12 de Oct. de 2023
Editada: Thanacha Choopojcharoen
el 12 de Oct. de 2023
I wrote a vectorized version of skew where v can be 3xn or nx3. This will return 3x3xn. Technically, this can be defined as a one-line anonymous function as well.
function S = skew(v)
a = size(v,1)==3;
n = size(v,round(1+a));
V = permute(v,[round(2-a),3,round(1+a)]);
I = repmat(eye(3),[1,1,n]);
S = cross(repmat(V,[1,3]),I);
end
Respuesta aceptada
Sean de Wolski
el 18 de Jun. de 2014
X=[0 -x(3) x(2) ; x(3) 0 -x(1) ; -x(2) x(1) 0 ];
3 comentarios
John D'Errico
el 19 de Jun. de 2014
A great virtue of MATLAB (ok, almost any programming language) is the ability to write functions that do what you want. Making a skew-symmetric matrix from a vector is not something most people will ever need to do, so it is unlikely you would find a simple command to do it. However, since you can write functions that do anything you want, anything that you will do often, then do so. Personalize your version of MATLAB to include such tools that do what you have a need for.
In this case, a simple m-file would suffice. Or write a function handle if this is not something you will have a need for beyond today.
Finally, the code that Sean gives is easily vectorized to create a 3-d array, where each plane would be one such matrix.
Más respuestas (3)
Sergei Sergienko
el 5 de Jun. de 2020
Editada: Sergei Sergienko
el 5 de Jun. de 2020
There is special function for this in Matlab called skew
v = [1 2 3]';
skew(v)
ans =
0 -3 2
3 0 -1
-2 1 0
2 comentarios
Mitsu
el 3 de Dic. de 2020
This function is not included, as of MATLAB 2019b; unless it is part of a specific additional toolbox.
Elyar Zavvari
el 12 de Ag. de 2021
You will find this function in matlab robotics toolbox by Kevin Lynch.
Raul Cajias
el 20 de Abr. de 2016
I think what you're looking for is the skewdec skewed function. However it's only available with the 'Robust Control Toolbox'.
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